In a long wave infrared (LWIR) system there is the need to capture the maximum amount of information of objects over a broad volume for the identification and classification by the human or machine observer. In a trad...
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ISBN:
(纸本)0819457698
In a long wave infrared (LWIR) system there is the need to capture the maximum amount of information of objects over a broad volume for the identification and classification by the human or machine observer. In a traditional imaging system the optics limit the capture of this information to a narrow object volume. This limitation can hinder the observer's ability to navigate and/or identify friend or foe in combat or civilian operations. By giving the observer a larger volume of clear imagery their ability to perform will drastically improve. The system presented allows the efficient capture of object information over a broad volume and is enabled by a technology called wavefront coding. A wavefront Coded system employs the joint optimization of the optics, detection and signal processing. Through a specialized design of the system's optical phase, the system becomes invariant to the aberrations that traditionally limit the effective volume of clear imagery. In the process of becoming invariant, the specialized phase creates a uniform blur across the detected image. Signal processing is applied to remove the blur, resulting in a high quality image. A device specific noise model is presented that was developed for the optimization and accurate simulation of the system. Additionally, still images taken from a video feed from the as-built system are shown, allowing the side by side comparison of a wavefront Coded and traditional imaging system.
Classical optical design techniques are oriented toward optimizing imaging system response at a single image plane. Recently, researchers have proposed to greatly extend the imaging system depth of field, by introduci...
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ISBN:
(纸本)0819440833
Classical optical design techniques are oriented toward optimizing imaging system response at a single image plane. Recently, researchers have proposed to greatly extend the imaging system depth of field, by introducing large deformations of the optical wavefront, coupled with subsequent post-detection image restoration. In one case, a spatially separable cubic phase plate is placed at the pupil plane of an imaging system to create an extremely large effective depth of field. The price for this extended performance is noise amplification in the restored imagery relative to a perfectly focused image. in this paper we perform a series of numerical design studies based on information theoretic analyses to determine when a cubic phase system is preferable to a standard optical imaging system. The amount of optical path difference (OPD) associated with the cubic phase plate is directly related to the amount of achievable depth of field. A large OPD allows greater depth of field at the expense of greater noise in the restored image. The information theory approach allows the designer to study the effect of the cubic phase OPD for a given depth of field requirement.
We investigate the depth of field (DoF) enhancing capacity of binary annular phase masks embedded in panchromatic imaging systems. We first demonstrate with numerical simulations and real-world imaging experiments tha...
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We investigate the depth of field (DoF) enhancing capacity of binary annular phase masks embedded in panchromatic imaging systems. We first demonstrate with numerical simulations and real-world imaging experiments that phase masks optimized for monochromatic illumination are somewhat robust to their use under wide spectrum illumination: they provide images that are slightly less sharp but less affected by deconvolution artifacts due to spectral averaging. Then, we show that masks specifically optimized for wide spectrum illumination perform better under this type of illumination than monochromatically optimized phase masks under monochromatic illumination, especially when the targeted DoF range is large. This interesting effect comes from the fact that deconvolution artifacts are significantly reduced by wide spectrum illumination. These results show that it is useful to take into account the illumination spectrum together with the scene characteristics and the targeted DoF range for effective codesign of DoF enhancing imaging systems. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)
We experimentally investigate the performance of co-optimized hybrid optical-digital imaging systems based on binary phase masks and digital deconvolution for extended depth-of-field (DoF) under narrowband illuminatio...
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We experimentally investigate the performance of co-optimized hybrid optical-digital imaging systems based on binary phase masks and digital deconvolution for extended depth-of-field (DoF) under narrowband illumination hypothesis. These systems are numerically optimized by assuming a simple generic imaging model. Using images of DoF targets and real scenes, we experimentally demonstrate that in practice, they actually reach the DoF range for which they have been optimized. Moreover, they are shown to be robust against small mask manufacturing errors and residual spherical aberration in the optical system. These results demonstrate that the optical/digital optimization protocol based on generic imaging model can be safely used to design DoF-enhanced imaging systems aimed at real-world applications. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)
For many practical applications of image sensors, how to extend the depth-of-field (DoF) is an important research topic;if successfully implemented, it could be beneficial in various applications, from photography to ...
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For many practical applications of image sensors, how to extend the depth-of-field (DoF) is an important research topic;if successfully implemented, it could be beneficial in various applications, from photography to biometrics. In this work, we want to examine the feasibility and practicability of a well-known "extended DoF" (EDoF) technique, or "wavefront coding," by building real-time long-range iris recognition and performing large-scale iris recognition. The key to the success of long-range iris recognition includes long DoF and image quality invariance toward various object distance, which is strict and harsh enough to test the practicality and feasibility of EDoF-empowered image sensors. Besides image sensor modification, we also explored the possibility of varying enrollment/testing pairs. With 512 iris images from 32 Asian people as the database, 400-mm focal length and F/6.3 optics over 3 m working distance, our results prove that a sophisticated coding design scheme plus homogeneous enrollment/testing setups can effectively overcome the blurring caused by phase modulation and omit Wiener-based restoration. In our experiments, which are based on 3328 iris images in total, the EDoF factor can achieve a result 3.71 times better than the original system without a loss of recognition accuracy.
Strong infrared radiation interference is a common type of interference in optoelectronic countermeasures. An optical system exposed to strong light would disrupt the acquisition of image information and even damage t...
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ISBN:
(纸本)9798400709388
Strong infrared radiation interference is a common type of interference in optoelectronic countermeasures. An optical system exposed to strong light would disrupt the acquisition of image information and even damage the device. In this paper, we aim to design an infrared system for object detection under the circumstances of strong infrared radiation interference in order to enhance the countermeasure capability of the optoelectronic system. Firstly, we introduce the Wave-front coding (WFC) technique to attenuate the damage caused by strong infrared radiation interference. Secondly, we use L₂ (Tikhonov) regularization to restore the blurred image caused by wavefront coding and obtain a clear low-light image. Thirdly, we use Recursively Separated and Weighted Histogram Equalization (RSWHE) for image enhancement to improve its contrast. Finally, we use the YOLOv8 algorithm for object detection. Experiments on real infrared images show that this scheme has outstanding performance under strong infrared radiation interference.
An incoherent optical system with wavefront coding extends the depth of field (DOF) by employing a cubic phase plate (CPP). We designed a digital microscope with a CPP in the aperture stop and on the surface of the le...
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An incoherent optical system with wavefront coding extends the depth of field (DOF) by employing a cubic phase plate (CPP). We designed a digital microscope with a CPP in the aperture stop and on the surface of the lens, which extended the DOF. In addition, we proposed a method in which the CPP can be shifted and assigned to the surface of the lens by adjusting the third-order coefficient of the xy polynomial surface, so that the CPP on the surface of the lens can replace a single CPP in the aperture stop, which collided with the optical elements and mechanism in some cases, to reduce the difficulty in assembling. The microscope with flexibility and without loss of the illumination level can considerably improve the efficiency of microscopic applications.
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